Generally, window shades are divided, depending upon their designs, into a curtain which is folded and unfolded leftward and rightward, a blind which has a plurality of slats capable of being adjusted in their inclination angle, a roll screen which has a sheet capable of being wound on and unwound from a rotation roll, and a roman shade which has a cloth capable of forming folds thereon when it is raised by manipulation of a cord.
Referring to FIG. 1 illustrating a conventional roman shade, an operation box 30 is provided at an end of a frame 10. In the operation box 30, a driving cord 25 is wound on a reel. While not shown in FIG. 1, the driving cord 25 is operatively connected with driven cords 22 each of which is fastened to a cloth 20 by the medium of rings at predetermined positions. If the driving cord 25 is manipulated to be moved upward and downward, the driven cords 22 are also moved upward and downward. In this way, in the conventional roman shade, the cloth 20 is raised and lowered using the driving cord 25.
However, in the conventional roman shade, a problem is caused in that, when the driving cord 25 is wound on and unwound from the reel to raise and lower the cloth 20, since portions of the driving cord 25 are overlapped one on another on the reel, the cloth 20 is likely to be maintained in an unbalanced state.
The conventional roman shade uses the driving cord 25 which is formed of yarn or fabric tape. In the case that the driving cord 25 is formed of yarn, while the cloth is raised and lowered, the driving cord 25 is apt to get entangled. This being the case, if the driving cord 25 is not appropriately disentangled, the driving cord 25 should be replaced with a new one. In the case that the driving cord 25 is formed of fabric tape, the fabric tape is wounded in a groove which is defined on a rotation gear, but the fabric tape is apt to be jammed in the groove.
Another roman shade is disclosed in the art. In this roman shade, an operation box is provided at an upper end of the roman shade. In the operation box, a chain is wound on a shaft, so that a cloth can be raised and lowered as a user pulls down one or the other portion of the chain. In the prior roman shade employing this type of chain, when a cloth is stopped in its movement after being raised or lowered through manipulation of the chain, the cloth is likely to sag from its own weight. In consideration of this fact, in the another roman shade, the chain is hooked on a ring secured to the operation box so as to prevent the cloth from sagging. Nevertheless, in this roman shade, defects are caused in that the procedure for hooking the chain on the ring every time the cloth is moved to a desired height is bothersome.
To cope with these defects, the present applicant disclosed in Korean Utility Model Registration No. 179141 a head rail for a roman shade, in which the driving cord and the driven cords are replaced with ball chains. The power transmission between the driving cord and the driven cords is converted into that between a rotation gear and a rotation shaft, so that the cloth can be maintained in a balanced state and entanglement between the driving cord and the driven cords can be avoided. Also, the present applicant disclosed in Korean Utility Model Registration No. 267467 an operation box for a roman shade, which is constructed to prevent the cloth from sagging from its own weight when the chain is pulled down to raise the cloth and then released.
While the head rail and the operation box effectively solve the defects caused in the conventional roman shade, it is still necessary to change a shape of the rotation gear, improve operational reliability of the ball chain, prevent noise generation while keeping the cloth from sagging, and allow the cloth to be easily cleaned.